The invention relates to an efficient dephosphorization smelting method in a medium phosphorus hot metal converter, which mainly solves the technical problems that the existing dephosphorization agent contains large amount of fluorites, the environmental pollution is easy to be caused, the smelting cost is too high, etc. The smelting method comprises the steps as follows: (a) the top-bottom composite smelting is adopted, the material components of metal main material which is put in have the weight percentage that the molten iron is 85 to 93 percent, and scrap steel or pig irons are 7 to 15 percent; (b) the dephosphorization smelting oxygen is controlled in the prior period; (c) slagging material containing MgO is added at the back part of a downwards-blowing gun, wherein, quicklime is added to control the binary basicity to range from 2.0 to 3.0, and iron ore is added in to adjust the slag discharge temperature in prior period until the temperature reach 1470 DEG C; (d) the slag discharge control in the dephosphorization prior period comprises the steps that the oxygen blowing quantity is controlled to be about two fifth of the oxygen blowing quantity in normal converting, the converting time is 3 to 6 minutes, and slag preventer is added in before slag discharge, wherein, the quantity of the slag preventer is 200 to 500kg; (e) later dephosphorization control has the steps that the oxygen blowing quantity is controlled, the quicklime needs to be added in order to accelerate the slag melting, the iron ore is added in to control the end point temperature to be less than or equal to 1650 DEG C. The efficient dephosphorization smelting method is suitable for a large converter to execute the deep dephosphorization smelting.